Coevolution between plants and herbivores is a classic. By comparison, coevolution between prey and predators is far less studied, probably because animal tissues are seen as less challenging food sources than plant tissues. The former are rich in nutrients and easily digestible while the later are full of indigestible fibres and toxic secondary compounds. However, the consumption of prey entails strong enough constraints that select for adapted life-histories among predators. My preferred organisms to address the question of life-history evolution are ladybird beetles (Coccinellidae) and their prey, aphids and coccids. The interactions between these insects are original because aphids are highly ephemeral resources contrary to coccids. Therefore, the comparison of species of ladybirds that feed either on aphids or coccids provides cues to envision how their life-history traits evolve.
Aphids and coccids live in groups. They form populated colonies that attract many predators and parasitoids. As a result, intra and interspecific competitions are intense among consumers. Among the Coccinellidae, natural selection favours individuals that select colonies that are not yet exploited. Some species of ladybird beetles that specialized in the exploitation of ephemeral resources rely on chemical cues to assess the quality of patches of prey. Ladybirds avoid laying eggs near aphids where conspecifics left a chemical trail when walking to catch prey. However, recent works in my laboratory indicate that the intensity of this behaviour varies depending on species. We are actually trying to understand why this is so.
Alexandra Magro is my closest partner in this exploration of the evolutionary dimensions of the interactions between ladybirds and their prey. In addition to the above research topics, we also are interested in using ladybirds as models to address several evolutionary questions, such as the evolution of maternal effects (in collaboration with Philipp Heeb) or why some species are more likely to quickly colonize new territories than others.
Waking up to ecology
My first job was as a teacher in zoology in an agricultural technical school, in Belgium. It was in 1978 already. I was not very happy because my students dislayed a low interest in animals. Most of them were sons of farmers that just wanted to know which pesticide they should use to get rid of these creepy crawlies threatening their father’s crops. I was not at all at ease with pesticides. I had lost my mother some years ago ; she died from a breast cancer. While trying to understand why my mother passed away so young, I learned that pesticides are among environmental factors that may trigger cancer. Therefore, my mood was tuned to biological control. I decided to set up a ladybird beetle culture to convince my students that predators have the potential of controlling pests. However, I never succeeded in having a decent ladybird culture. When trying to understand what went wrong, I discovered that biological control was and still is far more complex than I expexcted. As a consequence I decided to go back to university to start a PhD on the relationships between ladybirds and aphids. It was during my thesis that I became convinced that successful biological control only can exist if one understands the evolutionary strategies that respectively shaped the life-history strategies of pests and natural enemies and as a consequence interactions between these organisms. This is still a major backbone of my interest in nature.
See my publication list at [http://www.publicationlist.org/jean-louis.hemptinne]